Gas anchors

ABSTRACT

A gas anchor in combination with a downhole pump. The anchor has an upper terminal end connected to a pump intake and a lower terminal end in the form of an inverted cone from which there upwardly depends a skirt member which forms an annulus therebetween. An inverted frustum of a cone circumferentially encloses a marginal portion of the tubular body and forms a conical annulus therebetween with the second annulus being spaced apart from the first annulus by guide means. Apertures placed in communication with each annulus provides a liquid flow path to the pump to enable gas to be separated from liquid as flow occurs into the tubular body.

United States Patent Primary Examiner-James A. Leppink Attorney-MarcusL. Bates ABSTRACT: A gas anchor in Combination with a downhole pump. Theanchor has an upper terminal end connected to a pump intake and a lowerterminal end in the form of an inverted cone from which there upwardlydepends a skirt member which forms an annulus therebetween. An invertedfrustum of a cone circumferentially encloses a marginal portion of thetubular body and forms a conical annulus therebetween with the secondannulus being spaced apart from the first annulus by guide means,Apertures placed in communication with each annulus provides a liquidflow path to the pump to enable gas to be separated from liquid as flowoccurs into the tubular body.

PATENTEDuuv 9 usm /N VE/V TOE. HARRY GCAMBERN BY MARCUS LBATES H/sflGENT BACKGROUND OF THE INVENTION It is a common practice to employafonn of gas anchor in conjunction with a downhole production pump so asto preclude admixture of gas with the liquid flowing from a productionformation into the suction of the pump. When the gas anchor is affixedto the lower terminal end of the working barrel of the pump, and thepump is run into-the hole, various expedients incorporated into theanchor efiect a separation between the gas and oil by causing the oil toflow along a particular flow path. The separated gas moves upward byreason of its lower density and generally escapes through or into thespace between the casing and the tubing and hence through the sideoutlet of the well head.

in lowering a string of tools into a borehole with the gas anchor placedin underlying relationship with respect to the pump, and where parafiinhas accumulated within the borehole, difficulty will be experienced whenthe pumping operation is initiated for the reason that the pump willoften be plugged with this waxy residue. Various expedients haveheretofore been proposed in order to prevent the occurrence of suchplugging, such as, for example,.the provision of a brittle cast irondisc member that can be broken out by dropping a weight down through thetubing from the surface.

It is therefore desirable to provide an efiicient gas anchor whichseparates gas from the liquid which flows into the suction side of adownhole pump. It is also desirable to provide a SUMMARY OF THEINVENTION The present invention broadly comprehends an improved gasanchor for use in combination with a downhole pump with the anchoreffecting a separation between the gas and liquid so as to precludeadmission of gas to the working barrel of the pump. More specifically,the invention comprehends an elongated tubular body axially aligned withthe borehole and the pump and placed in underlying relationship withrespect to the pump intake so that fluid flow through the pump must alsooccur through the tubular body. The separation of the gas from theliquid is effected by two annular areas spaced apart from each other byguide means. The lowermost annulus is formed by an upstanding skirtmember which terminates in a cone with the apex of the cone forming thelowermost portion of the anchor. The second annulus is in the fonn of aninverted frusto cone which provides an inverted conical annulus.Apertures formed within a sidewall of the tubular body communicates eachof the annular areas with interior of the tubular body.

Upon the anchor being run into the hole on the end of a pump or pumptubing, the anchor penetrates a strata of wax, whereupon the aperturesassociated with the anchor are protected by the members forming theannular areas so as to preclude entrance of the wax into the anchorinterior. After the pump is set in place and production initiated, fluidflow must occur about the outer members forming the annular areasthereby causing separation of the gas and liquid to occur because of thevelocity of the fluid together with the lower density of the gas. Thisaction causes the separated gas to flow upward about the exterior of theanchor while liquid flows into the tubular body of the anchor and intothe suction area of the downhole pump.

It is therefore a primary object of the present invention to provide animproved gas anchor.

Another object of the present invention is the provision of a gas anchorwhich can satisfactorily penetrate wax formations located within aborehole.

A still further object of the present invention is the provision of agas anchor which effects separation between liquid and gas moreefiiciently than gas anchors of the prior art.

A still further object of the present invention is the provi sion of agas anchor which is low in cost, efficient in separation, simple indesign, and rugged in construction.

These and various other objects and advantages of this invention willbecome readily apparent to those skilled in the art upon reading thefollowing detailed description and by referring to the accompanyingdrawings.

BRlEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRlPTlON OF THE PREFERREDEMBODIMENT Disclosed in FIG. 1 is a downhole pump assembly 10 belowwhich gas anchor 12 is disposed in underlying relationship. The gasanchor is connected to a shoe or collar 14 which in turn is connected tothe lowermost end portion 15 of the pump. A longitudinally extendingpassageway indicated by nu- 'meral 16 flow connects the gas anchor tothe pump suction or intake.

A polish rod 17 reciprocates the pump to cause well fluid to exit at 18.Wellhead 19 supports tubing 21 within which sucker rod 22 is disposed.The pumphousing 23 includes the piston, valves, and working barrel 24,25, 26, and 27 therein. the details of which are unnecessary to discusssince the specific pump along with its various mechanisms can take onseveral difierent forms and therefore is not considered a part of thepresent invention.

The gas anchor, which forms the essence of the present invention,includes a tubular body 28 which can be of any length, and is axiallyaligned with the borehole and with the pump. Optionally provided withinthe upper portion of the tubing which connects the anchor to the pump isa number of radially spaced-apart ports 29. Guides 30 are attached tothe tubular body and radiate therefrom. The guides have a majordimension in cross section which is substantially equal to the majordiameter of the inverted frusto cone 31.

A second guide means 32 is similar to the upper guide means and isattached to the tubular body at a location which separates the invertedfrusto cone from upstanding circumferentially disposed skirt member 33.The skirt member has a lowermost portion attached to an inverted conewhich terminates at apex 34 with the apex forming the lower extremity ofthe gas anchor.

The various members are welded together as indicated at 35, 35, however,those skilled in the art will realize that other fabrication techniquessuch as threaded connections can be substituted for some of the weldedconnections.

The inverted frusto cone upwardly diverges from the tubular body andterminates at edge portion 36. The lowermost portion of the frusto coneengages the upper extremity of a collar 37, although the collar 37 couldbe dispensed with and the tubular body could be one continuous length oftubular goods.

The skirt member terminates as a circumferentially extending edgeportion 38 which is spaced apart from the tubular body, and is attachedat 39 to the uppermost portion of the lower inverted cone. Centrallyaligned within the inverted cone is a collar 40 which is threadedlyconnected to and forms a portion of the tubular body. Triangular-shapedapertures 41 interconnect annular area 42 with the interior of thetubular body.

The inverted frusto cone forms a conical annulus at 43 with apertures 29flow connecting the annulus with the interior of the tubular body.

OPERATION The tubular body 28, which may be comprised of one or morejoints of tubular goods, is threadedly secured to the shoe or collar 14which forms the suction side of a downhole pump. As the downhole pumpand gas anchor assembly is run into the borehole, deposits of paraffinmay be encountered at some depth below the surface. The specific designand construction of the gas anchor precludes the pump intake from beingobstructed by the waxy deposits. In particular it will be noted thatapex 34 will penetrate a waxy formation while the skirt member 33prevents wax or paraffin deposits from entering triangular apertures 41.As the anchor penetrates the waxy formation, the inverted frusto cone 31prevents the paraffin from plugging the apertures 29'. The invertedcones usually clears a sufficient tunnel through the paraffin deposit sothat aperture 29 are unaffected by the deposits. However, should theuppermost apertures 29 become plugged as the pump continues its traveltoward the bottom of the borehole, experience shows that the apertureare soon cleared of the deposit because of the solubility of thehydrocarbons with respect to the parafiins. As the assembly continuestraveling downhole, guides 3 and 32, which may be spaced apart from eachother a considerable distance, maintain the gas anchor centrally alignedwithin the borehole.

Separation between the gaseous and liquid phase of the hydrocarbonsflowing from the production formation is effected because of theparticular flow path the mixture must follow. In order for liquid toflow into apertures 41 the mixture of gas and liquid must first flowupwardly past apex 34 and skirt member 33. As the flow reverses itselfin a manner indicated by the arrow at number 42, the difference in thespecific gravity between the liquid and gas phase effects a firstseparation so that gas-free liquid enters apertures 41 while theseparated gas continues uphole within the annulus formed between the gasanchor and the casing. The lower extremity of the longitudinalpassageway of the gas anchor is now filled with liquid. As liquid andgas continues to flow up about the exterior of the gas anchor andinverted frusto cone 31, the liquid follows the flow path indicated bythe arrow at numeral 43 and accordingly the mixture is subjected to asecondary separation. The separated liquid enters apertures 29' whichcommunicates the interior of the gas anchor with the annulus. Theseparated gas continues uphole towards the foot of the pump.

Those skilled in the art will now realize that the separated gas isforced against the inside peripheral wall of the casing at a spacedapart distance away from the tubular body 28. Apertures 29 are presentas a safety feature in the event that the lowermost ports or apertures41 together with ports 29 should for some unforseen reason becomeclogged with debris. Should flow stoppage occur, it will become evidentbecause of the action of the downhole pump as it becomes locked withgas, thereby indicating that the entire apparatus must be removed fromthe borehole and serviced. it is highly unlikely that both lower portswill become plugged except under unusual conditions.

Accordingly, the present combination of a downhole pump and gas anchorprevents gaseous flow from a hydrocarbonproducing formation fromentering into the pump intake. The elongated tubular body of the gasanchor is axially aligned with the pump and provided with means at 14for connecting the upper terminal end of the anchor to the pump intake.The lower terminal end of the gas anchor at 34 is in the form of aninverted cone. A skirt member 33 is spaced apart from andcircumferentially encloses a lower marginal portion of the tubular bodyso as to form annulus 42 therebetween, with the skirt having an upperfree portion 42 and a lowermost edge portion at 39. The lowermost edgeportion is connected to the upper extremity of the last said invertedcone.

Inverted frusto cone 31 has a free upper edge portion 36 which is spacedapart from and circumferentially extends about the tubular body 28, withthe lowermost edge portion of the cone being attached to the tubularbody at a location 35 which is also spaced apart from the upper edgeportion 38 of the skirt member 33. A conical annulus 43 is formedbetween the frusto cone and the tubular body. Apertures 29 flow connectthe interior of the tubular body and the frustoconical annulus.Accordingly, production fluid must flow over the skirt member 38 inorder to flow into the annulus at 42 and over inverted cone member 31and into annulus 43 in order to enter apertures 29'. This action effectsa separation between the liquid and gaseous phase of the productionfluid flowing from a hydrocarbon-producing formation into the suctionend of the downhole pump.

Those skilled in the art will comprehend fabricating the present anchorinto a unitary device by welding and the like. Others will envisionfabricating the entire apparatus from plastic and plasticlike materialsand such changes in design and construction are considered obviousvariations of the present invention.

lclaim:

1. In combination with a downhole'pump, a gas anchor for preventinggaseous flow from a hydrocarbon-producing formation into the pumpintake;

said anchor having an elongated tubular body axially aligned with thepump; means connecting an upper terminal end of the anchor to the pumpintake; the lower terminal end of said anchor being in the form of aninverted cone;

a skirt member circumferentially enclosing and spaced apart from a lowermarginal portion of said tubular body to form an annulus therebetween,said skirt member having an upper free edge portion and a lowermost edgeportion, said lowermost edge portion being connected to the upperextremity of said cone; means forming apertures which flow-connect theannulus to the interior of said tubular body;

an inverted frusto cone having a free upper edge portion spaced apartfrom and circumferentially extending about said tubular body, thelowermost edge portion of said frusto cone being attached to saidtubular body at a location spaced apart from the upper edge portion ofsaid skirt member to thereby form a conical annulus therebetween; meansforming apertures which flow-connect the interior of said tubular bodywith the conical annulus, whereby:

liquid must flow over the skirt member and into the annulus in order toenter the lower apertures, and, liquid must flow over the inverted conemember and into the annulus in order to enter the upper apertures.

2. The combination of claim 1 and further including radially spacedapart guide means attached to said tubular body and located between saidskirt member and said inverted frusto cone; said guide means beingradially spaced apart and describing a diameter which is substantiallyequal to the diameter of said skirt member.

3. The combination of claim 1 wherein the skirt member has a diametersubstantially equal to the major diameter of said inverted frusto cone.

4. The combination of claim I and further including upper and lowerspaced apart guide mean attached to said tubular body;

said upper and lower guide means being spaced apart from one another bysaid inverted frusto cone;

said frusto cone and said skirt member being spaced apart from oneanother by said lower guide means.

5. The combination of claim 4 wherein said upper and lower guide meansinclude radially spaced apart planar members having a major diametersubstantially equal to the major diameter of said skirt members;

said skirt member having a major diameter substantially equal to themajor diameter of said frusto cone.

6. The combination of claim 1 wherein there is further included meansforming apertures within said tubular body at a location intermediatesaid frusto cone and the upper terminal end of said tubular body.

1. In combination with a downhole pump, a gas anchor for preventinggaseous flow from a hydrocarbon producing formation into the pumpintake; said anchor having an elongated tubular body axially alignedwith the pump; means connecting an upper terminal end of the anchor tothe pump intake; the lower terminal end of said anchor being in the formof an inverted cone; a skirt member circumferentially enclosing andspaced apart from a lower marginal portion of said tubular body to forman annulus therebetween, said skirt member having an upper free edgeportion and a lowermost edge portion, said lowermost edge portion beingconnected to the upper extremity of said cone; means forming apertureswhich flow-connect the annulus to the interior of said tubular body; aninverted frusto cone having a free upper edge portion spaced apart fromand circumferentially extending about said tubular body, the lowermostedge portion of said frusto cone being attached to said tubular body ata location spaced apart from the upper edge portion of said skirt memberto thereby form a conical annulus therebetween; means-forming apertureswhich flow-connect the interior of said tubular body with the conicalannulus, whereby: liquid must flow over the skirt member and into theannulus in order to enter the lower apertures, and, liquid must flowover the inverted cone member and into the annulus in order to enter theupper apertures.
 2. The combination of claim 1 and further includingradially spaced apart guide means attached to said tubular body andlocated between said skirt member and said inverted frusto cone; saidguide means being radially spaced apart and describing a diameter whichis substantially equal to the diameter of said skirt member.
 3. Thecombination of claim 1 wherein the skirt member has a diametersubstantially equal to the major diameter of said inverted frusto cone.4. The combination of claim 1 and further including upper and lowerspaced apart guide mean attached to said tubular body; said upper andlower guide means being spaced apart from one another by said invertedfruSto cone; said frusto cone and said skirt member being spaced apartfrom one another by said lower guide means.
 5. The combination of claim4 wherein said upper and lower guide means include radially spaced apartplanar members having a major diameter substantially equal to the majordiameter of said skirt members; said skirt member having a majordiameter substantially equal to the major diameter of said frusto cone.6. The combination of claim 1 wherein there is further included meansforming apertures within said tubular body at a location intermediatesaid frusto cone and the upper terminal end of said tubular body.